Lubricant and process for preparing same



Patented Dec. 31, 1946 2,413,311 LUBRICANT AND PIOCESS FOR PREPARINGCharles A. Cohen, Roselle Park, N.

J assignor to Standard 011 Development Company, a corporation ofDelaware No Drawing. Application October 8, 1943, Serial No. 505,507

14 Claims. (01. 260-504) This invention relates to an improved heavyduty lubricant and the process of its production. More particularly itis concerned with mineral oils which are compounded with theneutralization products of a group of oil-soluble sulfonic acids derivedfrom the sulfuric acid treatment of petroleum hydrocarbons, knowntechnically as mahogany sulfonate." A principal object of this inventionis the production of a certain type of purified mahogany sulfonate in apetroleum lubricating oil, in situ, using the lubricating oil as thesource of the organic radicals contained in the mahogany sulfonate.

The use of mahogany sulfonates as additives to lubricating oils has beenpracticed by the oil industry for some time. When added in an amount ofabout 0.1% up to about 2 or 3% by weight of the oil, the compositionexhibits improved lubricating properties especially in heavy dutyservice such as is encountered in Diesel engines, aircraft engines andthe like. Oils containing mahogany sulfonates have a detergent action Onthose parts of the engine that they lubricate and are capable of beingused under increased loads and temperatures without causing seizure ofhearings, or sticking of piston rings by formation of varnish.

Oils compounded with these sulfonates also act as rust preventives inthe engine during periods of quiescence.

The mahogany sulfonates used in this service have in the past beenobtained as a by-product from the manufacture of white oils, from whichthey are usually isolated as a sodium salt containin varying amounts ofinorganic salts, oil and other organic impurities. When the mahoganysulfonates are used as additives to lubricating oils it is generallypreferred to use the salts of the alkaline earths such as magnesium,calcium and barium. The conversion of the sodium salt to the calciumsalt for example, requires an additional series of chemicalmanipulations and purification steps and a further object of thisinvention is the production of the alkaline earth, or other metal saltsof the mahogany acids without preliminary isolation and purification asan alkali salt.

This invention is a continuation-in-part of my copending application U.S. Serial No. 371,777

filed December 26, 1940, which has matured into Patent No. 2,388,677,dated November 11, 1945, and is an extension of the basic principlesdisclosed in said application.

According to the present invention, a lubricating oil base stock whichmay or may not have been previously acid treated, deasphalted, dewaxedor extracted with solvents such as ketones, nitrobenzene, phenol,cresol, chlorex, etc., or which may be a distillate, neutral or brightstock or a mixture of these, but is still reactive with sulfuric acid,is treated with about 0.5% up to about by volume of sulfuric acid strongenough to form mahogany acids having an average combining weight inexcess of 400, This acid may vary in strength from 100% to fuming acidcontaining up to 25% S03, or the oil may be treated with S03 either inthesolid state or in the gaseous state, with or without gaseous diluent,within the range of temperature of 20 to 120 (3., 20 to C. being theusual range. and from subto super-atmospheric pressure. If acid of lowerconcentration than is used. the sulfonic acids formed are too low in'combining weight (i. e., 3'75 or even 350 or lower): whereas only thoseof 400 and'above'are suitable for this invention. The total quantity ofacid-treating agent may be used either in a single application or may besplit into a series of applications with intermediate batch orcontinuous settling of the sludge formed during the treating process.One may use either a single strength'of acid-treating agent for all ofthe applications or may us'e'a weaker acid for the early treats, or usesludge from the final treats for the first treats in a partialcountercurrent system of treating, or use a true countercurrent methodof treating. During this process of treating and settling, temperaturemay be maintained constant throughout the system or varied within thelimits indicated. Instead of separating the sludge by settling, acentrifuge may be used either alone or in combination with a partialsettler.

The oils which are preferred for acid treating in the practice of thisinvention may vary in viscosity from about 50 to 1000 seconds Saybolt at100 F. and may be predominantly parafiinic, naphthenic or aromatic incharacter. When treating oils of high viscosity, a diluent may be addedwhich may be hydrocarbon in character or other organic liquid which isnot materially attacked during the process of acid treatment. Whentreating lighter oils, one may add varying percentages of extractsrecovered from other oils, such extracts generally being predominantlyaromatic in character, so as to enhance the yield of mahogany acidsrecoverable, either by a process of direct sulfonation. .or alkylationor both. :The oil should contain hydrocarbons which on reaction with100% or stronger acid will yield sulfonic acids having an averagecombining weight of 400 or higher.

when a petroleum lubricating oil has been treated with sulfuric acid inthe manner and under the conditions described above, two major productsare formed. The lesser in importance consists of a lower sludge layercomprising asphaltic material, tar, unreacted sulfuric acid and a groupof water-soluble sulfonio acids known as "green" or black acids. Theother product consists of an upper oil layer which, when separated fromthe sludge by decantation or the like, is strongly acidic in nature dueto dissolved sulfur dioxide and a group of oil-soluble sulfonic acidsknown as "mahogany acids, and is black to reddish brown in color andnearly opaque due to suspended and colloidally dispersed globules orparticles of sulfuric acid and water-soluble sulfonic acids, sludge andtar. The latter group of acids, sludge and tar which remain suspended inth' acid oil after the major portion of the sludge has separated out bysettling is known collectively as "pepper sludge."

If an acid oil prepared as above is neutralized while containingdissolvedsulfur dioxide and sulfonic acids, and also suspended peppersludge, with an alkali or alkaline earth oxide, hydroxide or carbonatefor example, the corresponding alkali or alkaline earth salts areformed, including normally water-soluble sulfates, sulfites, andwater-soluble sulfonates, part of which remains peptized in the oilbecause of the presence of the dissolved mahogany sulfonate formed andis not readily removed by filtration. The neutralization products of thetorial power and are largely responsible for the characteristic reddishbrown color of ordinary commercial mahogany sulfonates. Once formed theyare difiicult to remove. While the poorer color is objectionable, thechief objection to the inclusion of the sulfites and the neutralizationproducts of the pepper sludge in the oil is their harmful effect on thelubricating oil and engine and their instability during use, especiallyat the higher temperatures encountered in modern engine operation.

One of the major objects of this invention is to prepare lubricatingoils by the neutralization with a polyvalent metal, e. g. alkalineearth, of a sulfuric acid treated petroleum hydrocarbon containing thedesired mahogany acids, which has been entirely freed of sulfur dioxideand "pepper sludge" prior to neutralization.

According to the present invention, a sulfuric acid-treated oil, aftersubstantial removal sludge by settling or by centrifuging but beforeneutralization, is treated with a finely divided precipitant such as oneselected from the group comprising filter aids of diatomaceous origin,materials of siliceous origin such as tripoli or finely ground silica,or activated carbon, the finely divided pepper sludge complex removed bysettling and/or by filtration, the dissolved sulfur dioxide removed, asby air blowing, or inert gas blowing or by vacuum stripping, and theresulting oil containing only mahogany acid, is neutralized by a basicsubstance containing the desired polyvalent metal. This process yieldsas product a refined lubricating solution of the desired mahoganysuifonate which is free of objectionable inorganic and organicimpurities, is clear and pale in color and shows improved stability athigh temperatures.

Materials of diatomaceous origin which are suitable for the practice ofthis invention a e epper sludge possess high tinc- 0f the ,sludge has arelatively commercially available as filter aids such as the J-M Celitesand "Filter Cels" or "Dica1ites. Either the natural dried and groundearth may be used or it may be calcined with or without alkali or may beacid treated and calcined. Materials of siliceous origin such as tripolior finely ground silica such as is used for polishing agents andcommercially available as Snow Floss" or Super Floss are suitable as isfinely ground carborundum. Another class of materials suitable for thepractice of this invention is finely ground carbon which may be natural,acid treated, or an activated type. Other materials of like nature maybe used but the above are the preferred types. Various finely groundclays, such as Attapulgus fines may on occasion he used under specialcircumstances but such materials as natural bentonite are not considereddesirable.

The filter aid is added to the acid oil in an amount of from 1 to 40lbs. per 1000 gallons of oil. The method of treating the oil with theabove substances may be either by the direct addition of these materialsto the oil in the form of a dry powder or by preliminary admixture witha portion of the clear oil to form a slurry which can then be pumpedinto the main body of the oil. The oil, after the addition of the filteraid, may be agitated for a period of from 5 minutes to onehalf hour. If,for example, filter aid has been used, the filter aid-pepper sludgecomplex is then removed either by settling, or filtering, or both.

It filtering alone is used, it may be done with conventional filterpresses such as the plate and frame press or with a continuous rotarytype of press. It is advantageous when using a filter press to precoatthe press with filter-aid in the proportion of 5 to 10 lbs. of filteraid for every one-hundred square feet of filter press area. If settlingis the means used for removing the filter aid-pepper sludgecomplex fromthe acid oil, it may be accomplished by running the acid oilfilter aidmixture into a settling drum at a rate designed to give the oil asettling time of from 5 minutes to one hour. A combination of settlingand filtration may be used in that the oil after treatment is given asettling time sufficient to drop most of the filter aid-pepper sludgecomplex out and is then finished by filtering either wtih or without theaddition of more filter aid. An alternate method of separating thefilter aidpepper sludge complex from the oil is by means of a centrifugesuch as a basket type or one capable of discharging a slurrycontinuously.

No attempt is made here to postulate a theoretical mechanism for theoperation of this invention but the diversity of materials which aresuitable for the practice of this invention and the rapidity with whichagglutination or clumping of the pepper sludge particles takes placeafter the filter aid or tripoli, etc., has been added, withoutdiminishing within the limits of experimental error the originalmahogany acid content of the acid oil, has led to the assumption thatthe phenomenon represents a mutual coprecipitation of oppositely.charged colloidal particles. An unexpected result in the practice ofthis invention is that within certain limits, the less filter aid isused, the more rapidly does the filter aid-pepper sludge complex settle.This is thought to be due'to the fact that the pepper high density andwhen precipitated with the filter aid. the less the amount of filter aidused the higher the resultant density.

As will be apparent to those skilled in the acid-treating art, theprecise conditions of acid strength, volume of acid applied to the oil,temperature of treating, time of contact and possible use of diluentused in the acid treatment of the lubricating oil will vary within thelimits specified, depending on viscosity of the oil used. degree andmethod of preliminary refinement if applied before acid treatment,physical characteristics of the oil such as specific gravity, anilinepoint, viscosity index, etc., and chemical characteristics such asunsaturation, and various proportions, of parafilns, naphthenes andaromatics present. Moreover, the final concentration of mahogany soapand the characteristics of the oil obtained after treating areprofoundly infiuenced by the exact method of treating. Therefore theexact conditions for acid treating any particular oil are bestdetermined by experiment and such variations introduced as to make thebest use of the equipment at hand. Most oils will, however, follow ageneral pattern of behavior when acid treated. It is found forexample,-between the limits of temperature indicated, that for a givenoil and acid strength, a particular quantity of acid will form nearlythe same amount of mahogany soap. However, the distribution of themahogany soap between the oil and sludge layers appears to be a functionof the temperature used for treating. At low temperatures, such as C. or30 C., the partition of the mahogany acid in the direction of. thesludge is favored, but as the temperature is raised,

the solubility of the mahogany acid in the oil phase is favored to theextent that it is possible to treat under conditions where only tracesof mahogany acid remain in the sludge. With a rise in temperature oftreating to about 70 C. or 80 C., the sludge concommittantly releasessome oi1 which is normally held in solution by the mahogany acidcontained in the sludge, so that in general somewhat higher yields ofoil are likewise obtained when the oil is treated at higher temperature.

The following examples will illustrate the efiect of the acid treatingtemperature on the yields of refined oil and mahogany soap.

An oil having a 105 sec. Saybolt viscosity at 100 F. of Mid-Continentorigin, which had been dewaxed to 0 F. pour point, was treated with atotal of 21% by volume of free S03 fuming sulfuric acid in 3substantially equal dumps at C. and in one case at 70 C. in another. Theyields of products obtained are shown in the table below, expressed involume or weight percent based on the original oil distillate.

Oil soluble sulfonate distribution Mahog. sul- I Sulfonatc in fonate inoil Total sulfonate Temp. of treat sludge, weight mahog. weight producedper cent on dist. per cent on The ,extent to which advantage can betaken of the higher oil and mahogany sulfonate yield obtained by hightreating temperatures may be limited by the character of the distillateor oil treated. As noted above, when treating at higher 1 temperature,the sludge is de-oiled and may become too stiff to move through ordinarypipe lines or may have a tendency to coke on exposure to air. This isespecially true of straight run distillates of high viscosity whichcontain much asphaltic material. The tendency to form a stiff sludge inthe early treats given such an oil, can be prevented to a large extentby using somewhat lower temperature and weaker acid strengths. Afteracid treating, contacting with filter aid. or equivalent, and settlingor filtering, the acid oil is entirely free of pepper sludge andcontains the original amount of mahogany acids present along with acertain amount of dissolved sulfur dioxide.

The sulfur dioxide is then removed by airblowing, or by countercurrentair or inert gas stripping in a packed or bubble plate column, or theacid oil may be subjected to vacuum at ordinary or elevated temperaturesby means well known to the art. The removal of the sulfur dioxide may bemade an inherent feature of the filtration step in that the filtrationmay be run under vacuum such as is commonly done in the laboratory in aBuchner funnel or a combinaon hydrolysis or decomposition yields anoxide,

hydroxide or carbonate selected from the metal whose mahogany soap isdesired. The base may be added either in the form of a dry powder,aqueous solution or suspension, or dissolved or dispersed in an alcohol,naphtha, or lubricating oil which may or may not be volatile atmoderately elevated temperatures. I may use metallo-organic compoundswhich on hydrolysis or thermal decomposition will yield an oxide,hydroxide or carbonate capable of reacting with the mahogany acidpresent in the oil. Examples of materials which I may useforneutralization are magnesium, calcium, strontium and barium oxides,hydroxides or carbonates or mixtures thereof in aqueous solution orsuspension, or alcoholic solutions of certain of the above bases such asa methyl alcoholic solution of barium hydroxide, or these bases may bemixed or partially dissolved in high boiling alcohols such as oleyl oroctadecyl alcohol, or one may use metallo-organic compounds such ascalcium, magnesium or aluminum alcoholates. Basic compounds of Sn, Ni,

G0, etc., may also be used; The mixture of refined acid oil-and basicsubstance may be heated, e. g., to C. or higher to insure completereaction. It is preferred to use an excess of basic substance,especially if of the insoluble type and then filter to remove unreactedneutralizing agent. For instance, the oil may be filtered through a bedof finely divided calcium oxide, -hydroxide, or -carbonate to convertall dissolved sulfonic acids into calcium sulfonates which remaindissolved, and to simultaneously insure that any trace of sulfur dioxideor sulfuric acid is converted into insoluble sulfite or sulfate andremoved by the filtration, or adsorption.

After neutralization, the water or solvent may be removed by means ofheat used with or without a gas stream or may be subjected to the 7action of heat and vacuum. In the case where solvents have been usedduring the acid treatment especially with high viscosity oils, theymaybe recovered after neutralization by stripping with steam or fire andsteam, or by the use of vacuum. In those cases where the acid treatmenthas been carried to the extent where the mahogany acid concentration isrelatively high, e. g., above 3% or 4% and perhaps as high as 10%, 15%or even 20%, or higher, a refined lubricating oil base stock (thesame asor different from the one treated) may be blended into the concentrateeither before or after final neutralization or removal of the water orsolvent, to make a finished blend having the desired concentration ofabout 0.1-3% of sulfonate.

These oils may, if desired, be further compounded with other additivessuch as oxidation inhibitors and the like. Lubricating oils made inaccordance with this invention are generally pale in color and show goodstability especially at high temperatures and hence possess valuableadvantages over oils made by compounding an ordinary pre-formedcommercial alkaline earth sulfonate with a separately refined oil.

The invention will be more clearly illustrated by the followingexamples:

Example 1 A 1000 gallon batch of an oil composed of a mixture of astraight run parafiinic distillate and a low pour coastal distillatehaving a viscosity of 105 seconds Saybolt at 100 F. was treated with 150gallons of acid sludge obtained fromfurther treatment of the same oilwith 20% fuming acid, at a temperature of 70' C. for 1 hour. The mixturewas allowed to settle for 12 hours and the acid oil removed from thesludge by decantation. 910 gallons of oil was recovered and was given asecond treat at 70 C. with 90 gallons of 20% S: fuming sulfuric acid andallowed to settle as before. After decantation from the sludge, 820gallons of acid oil was recovered. This oil was agitated for 15 minutesat a temperature of 25 C. with pounds of Johns Manville StandardFilter-Gel, filter pressed through a plate and frame press andcountercurrently air blown in a column packed with Raschig rings untilfree of sulfur dioxide.

Titration of a sample of the oil showed it to have an organic acidity of.154 Normal. 800 gallons of the oil was mixed in a heated agitator withan exact equivalent of 1.15 Normal methyl alcoholic solution ofBa(OH)2.8H2O. Heat was applied and the methyl alcohol and water slowlydistilled from the oil-mahogany soap mixture. When a temperature of 120C. was reached, a vacuum equal to 5 mm. of mercury was applied until nofurther loss of volatile material was observed.

A clear amber product was obtained which was neutral in reaction andwhich set to a gel on cooling. Analysis showed this product to containabout by weight of barium sulfonate. On dilution of this concentratewith a standard motor oil to a concentration of1.5% by weight of bariumsulfonate, a clear, stable solution was obtained which gave excellentperformance in the standard 36-hour Chevrolet engine test described inthe 1942 edition of A. S. T. M. Standards on Petroleum Products andLubricants, pages 28 to .42.

Example 2 An acid oil made from the same lubricating oil stock,and'treated in the same manner with acid as inExample 1, was neutralizedwith an aqueous slurry of calcium hydroxide. After neutralization andremoval of the water by heating. a slight haze due to the presence ofsiliceous matter in the lime, was removed by filtration. A clearconcentrate of calcium sulfonate of pale color was obtained, which whendiluted to a 1.0% by weight of solution in a standard motor oil gaze anexcellent performance in an engine The combining weight of the sulfonicacid is best determined by dissolving a sample of the sulfonic acid saltin 50% isopropyl alcohol, washing free of all oil by means of petroleumether, and converting to the potassium salt by treating with an excessof potassium carbonate. 0n evaporation of a sample of the alcoholicsolution of the potassium sulfonate, the product is obtained free of oiland inorganic salts. This purified sulfonate is ignited to potassiumsulfate and the average combining weight of the sulfonic acid calculatedfrom the following equation:

QRSOIK -----0 K1804 where R. is the organic group of the sulfonic acid.

It is not intended that this invention be limited to any of theparticular materials recited merely for the sake of illustration nor toany theory as the mechanism as to the operation of the invention, butonly by the appended claims in which it is intended to claim allmodifications coming within the scope and. spirit of the invention.

I claim:

l. The process which comprises contacting a finely divided siliceousfilter aid selected from the group consisting of diatomaceous' filteraids, tripoli, and finely ground silica, with an acidtreated oilcontaining pre-formed pepper sludge in dispersion, dissolved sulfurdioxide, and oilsoluble sulfonic acids having a combining weight of atleast 400 to co-precipitate the pepper sludge with the filter aid,removing co-precipitated pepper sludge and filter aid from the oil,removing dissolved sulfur dioxide from the oil, and thereafterneutralizing the oil-soluble sulfonic acids with a basic compound ofpolyvalent metal to form soluble sulfonates of said metal in theacid-treated oil from which pepper sludge and sulfur dioxide have beenremoved.

2. Process according to claim 1, in which the finely divided filter aidis a siliceous material of diatomaceous origin.

3. Process according to claim 1, in which the dissolved sulfur dioxideis removed from the oil by air blowing after removal of the peppersludge.

4. Process according to claim 1, in which the sulfur dioxide is removedfrom the oil under reduced pressure.

5. Process according to claim 1, in which the basic compound used forneutralizing the dissolved sulfonic acids in the oil is selected fromthe'group consisting of the oxides. hydroxides. and carbonates of thealkaline earths.

6. Process according to claim 1, in which the basic compound used forneutralizing the oilsoluble sulfonic acids in the oil is a basiccompound of calcium.

7. Process according to claim 1, in which the basic compound used inneutralizing the oilsoluble sulfonic acids is a basic compound ofbarium.

aaasn 8. Process according to claim 1. in which said basic-compound of apolyvalent metal used for neutralizing the oil-soluble suli'onic acidsisbarium hydroxide, and the barium hydroxide is dissolved in methylalcohol.

9. Process according to claim 1, in which the co-precipitated filter aidand pepper sludge are settled in the acid-treated oil and are removed bydecantation of the oil.

10. Process according to claim 1, in which the finely divided filter aidadmixed with the acidtreated oil is a material of diatomaceous originand is admixed in a proportion of 1 to 40 pounds per 1,000 gallons ofthe acid-treated oil to coprecipitate with the pepper sludge, and thecoprecipitated filter aid and pepper sludge are removed from theacid-treated oil by filtration.

11. The method of finishing a lubricating oil residual oil freed frompepper sludge until said residual oil is free from sulfur dioxide. and

neutralizing oil-soluble sulionic acids dissolved in the residual oil,freed from p pper sludge and sulfur dioxide, by reaction with apolyvalent metal base.

12. The process which comprises treating with a sulfuric acid of atleast 100% concentration a hydrocarbon lubricating oil which on reactionwith such acid yields oil-soluble sulfonic acids having an averagecombining weight of at least 400; removing resultant acid sludge untilthe residual acid-treated oil contains not more than 1% of sludge byvolumebut contains a small amount of colloidallydispersed pepper sludge,thereafter contacting the residual acid-treated oil with about 1 to40'pounds diatomaceous filter aid per 1,000 gallons of oil toprecipitate the pepper sludge, removing the precipitated pepper sludgeand the filter aid co-precipitated therewith, air-blowing the residualacid-treated oil until free from sulfur dioxide, then treating theresidual acid-treated oil, free from pepper sludge and from sulfurdioxide but still containing the oil-soluble sulfonic acids, with asubstantially equivalent amount of neutralizing basic compound ofcalcium to form a solution of oil-soluble calcium sulfonates in the oil.

13. Process according to claim 1 in which the filter aid is tripoli.

14. Process according to claim 1 in which the filter aid is finelyground silica.

CHARLES A. COHEN.

